Fig. 1. Structure of Nd:glass with cladding.

Fig. 2. Morphology of plastic scratch.

Fig. 3. Morphology of the plastic scratch.

Fig. 4. Changes in normalized scattering intensity at different incident angles.

Fig. 5. Schematic diagram of the experimental setup.

Fig. 6. Scattering powers of glass at different incident angles.

Fig. 7. (a) Average small signal gain coefficients and (b) gain uniformity of complete absorption and with residual reflection in cladding.

Fig. 8. Map of the single gridding region with subsurface defect.

Fig. 9. Equivalent residual reflectivity with the change of $n$.